It has been reported that a biofilm is a conglomerate of microbial organisms embedded in a highly hydrated matrix of exopolymers, typically polysaccharides, and other macromolecules (see U.S. Pat. Nos. 5,312,813 and 5,462,644, and references cited therein). Biofilms may contain either single or multiple microbial species and readily adhere to such diverse surfaces as river rocks, soil, pipelines, teeth mucous membranes, and medical implants. By some estimates biofilm-associated cells outnumber planktonic cells of the same species by a ratio of 1000-10,000:1 in some environments.
Prevention of colonization by and eradication of biofilm-associated microorganisms is an important, and often difficult to solve, problem in medicine. Unlike planktonic organisms, which are relatively susceptible to biocides, e.g., antibiotics, the structural matrix established during biofilm formation can make the colonizing cells able to withstand normal treatment doses of a biocide. It is known that when organisms are isolated from biofilms and then grown in planktonic culture, they lose many of the characteristics associated with the progenitor cells, in particular the ability to produce a glycocalyx. In the biofilm, the glycocalyx matrix appears to serve as a barrier which protects and isolates the microorganisms from host defense mechanisms, such as antibodies and phagocytes, as well as from antimicrobial agents including surfactants, biocides and antibiotics. The aforementioned patents report that in one study, biofilm-associated bacteria were able to survive a concentration of antibiotic 20 times the concentration effective to eliminate the same species of bacteria grown in planktonic culture.
Biofilm infections can occur in a variety of disease conditions. In some tissue infections, such as prostatitis, the infective bacterium is capable of growing in the infected tissue in both biofilm (sessile) and circulating (planktonic) form. Although growth of the planktonic cells can be controlled by antibiotic treatment, the biofilm itself may be refractory to treatment, providing, in effect, a reservoir of infection which can lead to recurrence of the infection after antibiotic treatment.
Biofilm formation can also be a serious complication in bioimplants, such as bone prosthesis, heart valves, pacemakers and the like. Biofilm formation on exposed surface of a bioimplant can degrade the function of the implant, as in the case of implanted valves, lead to serious joint or bone infections, as in the case of a bone prosthesis, and in all cases, provide a source of difficult-to-treat septic infection. In the case of heart valve endocarditis cases a surgeon is forced to dissect all infected tissue, treat locally with antibiotics and antiseptics followed by valve replacement. Unfortunately, the treatment is often unsuccessful over time due to perivalvular leak caused by a continuing infection. If the surgeon had a more effective method of treating the infection during surgery, valve replacement outcomes could be improved.
While U.S. Pat. No. 5,312,813 discloses in vivo treatment of a urinary tract infection, for example, there is no mention of the treatment of an infection during the course of surgery. U.S. Pat. No. 5,462,644 is similar in this regard. In both these patents, in vivo treatment may instead be accomplished by administering a biocide orally with electrical current then being applied across the area to be treated. Thus, the in vivo treatment in these cases is accomplished by non-invasive means and outside of the context of surgery.
The present inventor has recognized that a need exists to enable surgeons to treat infected areas during surgery to thereby enhance probabilities for success of re-implant of a bio-prosthesis. The present invention provides a solution to one or more of the disadvantages and deficiencies described above.